The present invention relates to builders' tools such as used in the construction trades for establishing parallel, perpendicular or just straight reference lines in laying out frameworks, walls, foundations and the like, and is more particularly directed to such tools incorporating a laser.
In various construction projects such as constructing the framework for a building, constructing masonry walls, or remodeling existing structures, it is often necessary to establish reference lines parallel or perpendicular to a specified line or surface, for example, to assure that adjoining walls will be perpendicular to one another and perpendicular to the floor and ceiling or to measure deviations from perpendicularity. Traditionally this has been accomplished by laying out reference lines with string lines using bubble levels or by marking off the reference lines with conventional carpenter's levels and squares. More recently, a number of devices have been developed that employ laser beams to define reference lines.
An early precursor of such devices employing a light beam instead of a laser is shown in U.S. Pat. No. 2,877,555 of Visockis. This device mounts an electric light and flashlight batteries within an elongated carpenters level so as to project a pencil-like "flashlight" beam of light out one end of the level. The beam is intended to extend the effective length of the level with the object of obviating the need to reposition the level continually when aligning a large number of elements extending over a distance much greater than the length of the level itself. The Visockis patent suggests that the device would be useful in such situations as laying a floor or vertically aligning a brick wall.
A later such device is disclosed in European patent application EP 0 401 815 of LAWA GmbH. This device includes a laser mounted much like the electric light of U.S. Pat. No. 2,877,555 in an elongated carpenter's level for projecting a beam out one end of the level.
PCT patent application Publication No. WO 91/02217 of Hinkel discloses a laser straightedge device in the form of an elongated carpenter's level that includes an optical arrangement for splitting the laser beam and deflecting it in several directions within the device housing so as to project two or three laser beams in perpendicular directions to one another.
U.S. Pat. Nos. 3,897,637 and 4,333,242 of Genho disclose more complicated level devices that include a laser simultaneously providing two or three beams at 90 degrees to one another. In these devices the perpendicularity of the beams is established with appropriate optics including one or more beam splitters for optically defining the perpendicular beams. The units include bubble levels and threaded leveling screws for leveling the beams. The device of U.S. Pat. No. 4,333,242 additionally includes a servomechanism responsive to a pair of level vials for automatically adjusting the disposition of the unit relative to the surface on which it rests until the axis of each level vial is horizontal.
Yet another known such laser referencing device is disclosed in French patent application FR 2 636 732 of Berny. The laser is mounted in an elongated tube, and the laser beam is separated into two perpendicular beams by a beam splitter, which is mounted for rotation on a motor so that one beam is perpendicular to and rotates about the axis defined by the second beam. The rotating beam thus defines a plane perpendicular to the axis defined by the second beam.
U.S. Pat. Nos. 4,912,851 of Rando et al. and 5,075,977 of Rando disclose more complicated leveling and alignment tools incorporating a diode laser. These tools include a tilt compensation mechanism for use on surfaces which are not level so that the device will nevertheless deliver a truly plumb or truly horizontal beam.
The above devices are subject to one or more of the following drawbacks or deficiencies. They are complex, requiring on-board optical arrangements of mirrors, prisms and/or beam splitters, sometimes even including motors for rotating an optical element. They may be undesirably large, inconveniently heavy, or cumbersome to use. They may be optically delicate in the sense that they may be undesirably easily knocked out of alignment, and may require careful alignment or leveling on each use. Some devices include on-board mechanisms for referencing the laser beam to the true horizontal or true vertical and not to the surface on which the device is positioned, and so these devices are not useful for establishing non-horizontal or non-vertical reference lines. In any case they tend to be costly to manufacture. Even the simple devices of U.S. Pat. No. 2,877,555 or European patent application EP 0 401 815 share a disadvantage with some of the more complex devices: The reference line they provide is not sufficiently accurate.